Abstract: This paper provides an evolutionary foundation for our capacity to attribute preferences to others. This ability is intrinsic to game theory, and is a key component of "Theory of Mind", perhaps the capstone of social cognition. We argue here that this component of theory of mind allows organisms to efficiently modify their behavior in strategic environments with a persistent element of novelty. Such environments are represented here by multistage games of perfect information with randomly chosen outcomes. "Theory of Mind" then yields a sharp, unambiguous advantage over less sophisticated, behavioral approaches to strategic interaction. In related experiments, we show the subscale for social skills in standard tests for autism is a highly significant determinant of the speed of learning in such games.